The present invention relates to a synthetic composite board product for use in the building and construction industry. Synthetic prefabricated boards frequently have strength, density, acoustic and fire resistant characteristics unavailable with conventional forest products. More recently, the ever dwindling supply of natural resources has made synthetic composite boards a cost effective alternative to conventional wood boards.
Various attempts in the prior art have been made to fabricate a composite panel embodying such characteristics as low density, improved isotropic mechanical properties, greater resistance to moisture and improved thermal and acoustical insulation qualities. Nevertheless, it has been customary to sacrifice strength to obtain low density or to sacrifice low density to obtain maximum strength.
Composite board structures have been prepared by combining synthetic resins with cellulosic waste material, such as wood shavings, paper scraps, sawdust, etc. Examples of these prior art devices are U.S. Pat. Nos. 3,598,672 to Heller, 2,951,057 to Weise, 4,324,831 to Parrini, 4,468,336 to Smith and 4,528,037 to Guidat. U.S. Pat. No. 3,598,672 discloses an insulation composition comprising textile fibers in conjunction with solid polystyrene which is subjected to high pressure in a mold. The binder may be an epoxy or polyster resin. U.S. Pat. No. 3,510,323 discloses the use of a silane ingredient to function as a binder for sawdust in an insulator material. U.S. Pat. No. 4,324,831 discloses a prefabricated panel combining wood chips and polystyrene. U.S. Pat. No. 4,528,037 discloses a thermal and acoustic insulation material which includes a lignocellulose material in combination with an alkali metal silicate solution. U.S. Pat. No. 2,806,509 to Bozzacco discloses a sandwich structure composed of polystyrene and silicone resin which yields individual, adjacently disposed beads for added strength after molding.
All of the aforementioned prior art composite boards either combine cellulosic filler material with a polymer or inorganic fillers, such as asbestos, various clays, calcium carbonate and the like, with foamable resins. None of the prior art patents disclose composite board product having sufficient interfacial bonding between the polymer and the filler to yield a composite board which exhibits relatively low density and increased mechanical strength. Furthermore, composite boards consisting of conventional cellulosic filler and foamed polymer lack resistance to thermal and solvent attack during lamination. The inability of the prior art boards to accept resinous laminates significantly reduces their utility in the industry.